The present invention relates generally to the field of optical switches, and more particularly to reflective-type optical switches for switching optical signals between any pair of optical ports to/from the switch interface.
With the increasing use of optical signals in telecommunications networks, the demand for high-bandwidth capable optical switches that can quickly route the optical signals along desired optical paths has increased. One type of optical switch converts an optical signal received on one optical port (e.g., an optical fiber end) to the switch interface to an electrical signal, switches the signal electronically, and re-converts the electrical signal to an optical signal output on a desired optical port (e.g., another optical fiber end) from the switch interface. Such optical switches are known as Optical Electrical Optical (OEO) switches. As may be appreciated, the bandwidth and switching speed capabilities of an OEO switch may be limited by the initial optical-to-electrical and subsequent electrical-to-optical signal conversions that are required.
A different approach to the switching of optical signals is known that overcomes the limitations of OEOs by switching the signals in the optical domain eliminating the optical-to-electrical and electrical-to-optical signal conversions. Such all optical switches are known in the art as Optical Cross Connect (OXC) switches. One type of OXC utilizes moveable reflectors (e.g., mirrors) to provide for the switching of optical signals within the free-space of the switch interface (i.e. without optical fibers, waveguides or the like). Typically such switches employ at least a pair of reflectors that are moved to respective orientations in order to provide an optical pathway within the free-space of the switch interface between any one of a plurality of input ports to the switch interface and any one of a plurality of output ports from the switch interface. As may be appreciated, an important parameter of such reflective-type free-space OXCs is the length of the path that an optical signal must traverse in order pass from one of the input ports to one of the output ports. Another parameter of importance to such reflective-type free space OXCs includes the proximity of the optical inputs and outputs to the reflectors, because as the distance between the reflectors and the inputs and outputs increases, there is less tolerance to alignment inaccuracies between the reflectors and the inputs and outputs.
Accordingly, the present invention provides a free-space optical cross connect for switching optical signals between optical signal ports to/from the switch interface. The optical cross connect of the present invention provides a compact switch wherein all of the moveable reflectors are supported on a single substrate. Having all of the reflectors supported on a single substrate provides for a minimal optical path length between a given pair of optical ports, and also permits the optical ports to be located in very close proximity to the reflectors. Having all of the reflectors on a single substrate also achieves advantages in the complexity of switch construction as it is not required that multiple substrates be properly oriented within the switch interface.
According to one aspect of the present invention, an optical cross connect for switching optical signals between a plurality of optical ports includes a substrate having a first surface facing the optical ports. A plurality of reflective microstructures are formed on the first surface of the substrate. Each reflective microstructure includes an optically reflective surface and is associated with one of the optical ports. Each reflective microstructure is positionable to orient its reflective surface to reflect an optical signal receivable from its associated optical port to the reflective surface of at least one other reflective microstructure. Each reflective microstructure is also positionable to orient its reflective surface to reflect an optical signal receivable from at least one other reflective microstructure to its associated optical port.
By properly orienting any pair of reflective microstructures on the substrate, an optical signal can be switched from any optical port to any other optical port. In this regard, the optical cross connect may further include a plurality of positioning systems formed on the substrate. Each positioning system is associated with one of the reflective microstructures and is operable to both elevate its associated reflective microstructure from the first surface of the substrate and tilt its associated reflective microstructure with respect to the first surface of the substrate with at least two degrees of freedom (e.g., about two substantially orthogonal axes). The reflective microstructures and their associated positioning systems may be respectively arranged and configured such that centers of the reflective surfaces of the reflective microstructures are aligned with central axes of their associated optical ports when the reflective microstructures are elevated at a specified height from the first surface of said substrate. This initial alignment helps maintain alignment of the optical signal beams with the reflective surfaces of the reflective microstructures as the reflective microstructures are tilted to redirect the optical signals since tilting of the reflective microstructures may result in small lateral movements of the centers of the reflective microstructures. Further, although many configurations are possible, the reflective surfaces of the reflective microstructures may, for example, be circular or elliptical in area. Employing elliptical reflective surfaces may provide for greater efficiency in the amount of optical energy that is reflected for the footprint area consumed by the reflective microstructures. This is because a typical telecommunications optical signal beam is circular in cross-section and thus has an elliptically shaped intersection with a flat surface intersecting the beam at an angle thereto.
If desired (e.g., to protect the surface of the substrate and the reflective microstructures and positioning systems formed thereon), the optical cross connect may further include a lid positionable between the optical ports and the first surface of the substrate. The lid may be hermetically sealed with the substrate to prevent the entry of contaminants into the switch interface. The lid is configured to permit transmission of optical signals therethrough between each optical port and its associated reflective microstructure. For example, the portions of the lid between the optical ports and the reflective microstructures may be made of an optically clear material.
The optical ports may comprise optical fiber ends that abut a side of the lid that faces away from the first surface of the substrate. In this regard, the lid may also facilitate alignment of the optical fiber ends with their associated reflective microstructures. For example, there may be a plurality of holes within which the optical fiber ends are receivable formed on the side of the lid facing away from the first surface of the substrate. The fiber end receiving holes can be arranged on the lid in a pattern appropriate to align the optical fiber ends with the reflective microstructures when the reflective microstructures are in a predetermined position (e.g., when the reflective microstructures are elevated at a specified height from the first surface of the substrate). Alternatively, the optical cross connect may further include one or more plates that are attachable to the lid. The plate(s) include a plurality of holes within which the optical fiber ends are receivable. The fiber end receiving holes in the plate(s) are arranged in a pattern appropriate to align the optical fiber ends with the reflective microstructures when the plate(s) are attached on the lid. Pins, grooves, notches or the like may be employed to ensure proper positioning of the plates when attaching the plates to the lid.
In addition to facilitating proper alignment of the optical fiber ends with the reflective microstructures, the lid may also be configured to provide for efficient transmission of optical signals to/from the optical fiber ends from/to the reflective microstructures. In this regard, there may be a plurality of lenses disposed on a side of the lid facing the first surface of the substrate. The lenses are arranged in a pattern corresponding with the fiber end receiving holes in the lid (or the fiber end receiving holes in the plates when attached to the lid). Sections of optical fiber cores may extend through the lid (and the plate(s) if attached) between the holes and the lenses. Each lens focuses an optical signal transmitted from its associated optical fiber end and section of optical fiber core into a free space optical beam for transmission through the switch interface to its associated reflective microstructure. Each lens also focuses a free space optical beam received from its associated reflective microstructure onto the section of optical fiber core for transmission through the lid into its associated optical fiber end. Numerous other lens locations are possible. For example, the lenses may be disposed within the fiber end receiving holes in the lid or within the fiber end receiving holes of the plate(s).
According to another aspect of the present invention, an optical cross connect for switching an optical signal between a first plurality of optical ports and a second plurality of optical ports includes a substrate having a first surface facing the first and second pluralities of optical ports. A first plurality of reflective microstructures are formed on the first surface of the substrate. Each of the reflective microstructures of the first plurality of reflective microstructures is associated with one of the first plurality of optical ports and includes an optically reflective surface. A second plurality of reflective microstructures are formed on the first surface of the substrate. Each reflective microstructure of the second plurality of reflective microstructures is associated with one of the second plurality of optical ports and includes an optically reflective surface. Each reflective microstructure of the first plurality of reflective microstructures is positionable to orient its reflective surface to reflect an optical signal receivable from its associated optical port to the reflective surface of at least one of the reflective microstructures of the second plurality of reflective microstructures and to reflect an optical signal receivable from the reflective surface of at least one of the reflective microstructures of the second plurality of reflective microstructures to its associated optical port. Each reflective microstructure of the second plurality of reflective microstructures is positionable to orient its reflective surface to reflect an optical signal receivable from the reflective surface of at least one of the reflective microstructures of the first plurality of reflective microstructures to its associated optical port and to reflect an optical signal receivable from its associated optical port to the reflective surface of at least one of the reflective microstructures of the first plurality of reflective microstructures. In this regard, the substrate may have positioning systems associated with each reflective microstructure formed thereon that are operable to elevate their associated reflective microstructures from the first surface of the substrate and tilt their associated reflective microstructures with respect to the first surface of the substrate with at least two degrees of freedom (e.g., about two substantially orthogonal axes).
The first and second pluralities of reflective microstructures may, for example, be arranged in a plurality of rows on the first surface of the substrate. In this regard, the reflective microstructures within an outer row may be elevatable to a greater height from the first surface of the substrate than the reflective microstructures within an adjacent inner row. For example, if there are four straight, parallel rows of reflective microstructures, the reflective microstructures in the two outer rows may be elevatable to a greater height from the first surface of the substrate than the reflective microstructures in the two adjacent inner rows so that the reflective microstructures in the outer rows can xe2x80x9clook overxe2x80x9d elevated reflective microstructures in the inner rows adjacent thereto. In one embodiment, this is accomplished by fabricating the positioning systems associated with the reflective microstructures in the outer rows to have longer length lever arms/pivot members than the positioning systems associated with the reflective microstructures in the inner rows. The reflective microstructures may also be arranged in other row-like manners such as, for example, one or more concentric arcs or a combination of straight rows and concentric arcs, as well as in non row-like patterns.
Each reflective microstructure of the first plurality of reflective microstructures must rotate through a range of tilt angles in order to reflect an optical signal to or receive an optical signal from any one of the reflective microstructures of the second plurality of reflective microstructures. Likewise, each reflective microstructure of the second plurality of reflective microstructures must rotate through a range of tilt angles in order to receive an optical signal from or reflect an optical signal to any one of the reflective microstructures of the first plurality of reflective microstructures. The required range of tilt angles for a given reflective microstructure may vary depending upon the position of such reflective microstructure on the substrate with respect to the other reflective microstructures. However, the positioning system associated with each reflective microstructure may be oriented on the substrate such that the required range of tilt angles is symmetric about an axis of symmetry of such positioning system. For example, the positioning systems may be rotated relative to the lines along which the rows of reflective microstructures are arranged. In this regard, the reflective microstructures at either end of a row of reflective microstructures may be rotated by a greater amount than the reflective microstructures towards the middle of the row.
According to a further aspect of the present invention, an optical cross connect for switching an optical signal between a first plurality of optical ports and a second plurality of optical ports includes a substrate having a first surface facing the first and second pluralities of optical ports. A first plurality of reflective microstructures are formed on the first surface of the substrate. Each reflective microstructure of the first plurality of reflective microstructures includes an optically reflective surface and is associated with one of the first plurality of optical ports. A second plurality of reflective microstructures are also formed on the first surface of the substrate. Each reflective microstructure of the second plurality of reflective microstructures includes an optically reflective surface and is associated with one of the second plurality of optical ports. The optical cross connect further includes an optically reflective area facing and spaced away from the first surface of the substrate. The optically reflective area is positioned for reflecting optical signals between the reflective surface of any one of the reflective microstructures of the first plurality of reflective microstructures and the reflective surface of any one of the reflective microstructures of the second plurality of reflective microstructures. Each reflective microstructure of the first and second pluralities of reflective microstructures is positionable to orient its reflective surface to reflect an optical signal receivable from its associated optical port to the optically reflective area and to reflect an optical signal receivable from the optically reflective area to its associated optical port.
When the optical cross connect includes a lid that is positionable between the optical ports and the first surface of the substrate, the optically reflective area may be provided on a side of the lid that faces the first surface of the substrate. In this regard, the lid may, for example, be configured for permitting transmission of optical signals therethrough between each optical port and its associated reflective microstructure by having first and second clear areas separated by the optically reflective area.
According to yet another aspect of the present invention, an optical cross connect for switching optical signals between a plurality of optical ports includes a substrate having a first surface facing the optical ports. A plurality of reflective microstructures are formed on the first surface of the substrate. Each reflective microstructure is associated with one of the optical ports and includes an optically reflective surface. A plurality of positioning systems are also formed on the first surface of the substrate. Each positioning system is associated with one of the reflective microstructures. Each positioning system is operable to elevate its associated reflective microstructure from the first surface of the substrate and tilt its associated reflective microstructure with at least two degrees of freedom with respect to the first surface of said substrate.
At least one of the positioning systems includes a first lever arm of a first length. The first lever arm of a first length is attached at a first end thereof to its associated reflective microstructure and at second end thereof to the substrate. At least one of the positioning systems includes a second lever arm of a second length. The second lever arm of a second length is attached at a first end thereof to its associated reflective microstructure and at a second end thereof to the substrate. The first and second lever arms are pivotable about their second ends to lift and/or tilt their associated reflective microstructure. In this regard, the positioning systems may include electrostatic actuators or other appropriate actuation devices operable to effect pivoting of the first and second lever arms about the second ends thereof.
The first and second lengths of the first and second lever arms, respectively, are different so that pivoting of the first and second lever arms through the same angular displacement achieves different vertical displacements of the first ends of the first and second lever arms with respect to the first surface of the substrate. In this regard, the first length may, for example, be between about 500 microns and about 1000 microns, and the second length may, for example, be between about 1000 and about 1500 microns. Having different length first and second lever arms allows the respective reflective microstructures associated therewith to be elevated to different heights from the substrate permitting one reflective microstructure to xe2x80x9clook overxe2x80x9d the other while applying the same level control signal to each positioning system. In this regard, the reflective microstructures may, for example, be arranged in a plurality of rows or arcs on the first surface of said substrate. The positioning systems associated with reflective microstructures in a first one of the rows or arcs may include first lever arms of a first length and the positioning systems associated with reflective microstructures in a second one of the rows or arcs may include second lever arms of a second length. Thus, upon application of the same level control signal, the reflective microstructures in the first row are elevated to one height from the substrate and the reflective microstructures in the second row or arc are elevated to a greater height (assuming the second length is greater than the first length) from the substrate thereby allowing the reflective microstructures in the second row or arc to xe2x80x9clook overxe2x80x9d the reflective microstructures in the first row or arc.
According to one more aspect of the present invention, an optical cross connect for switching an optical signal between a first optical port and any one of a plurality of second optical ports includes a substrate having a surface facing both the first optical port and the plurality of second optical ports. A first reflective microstructure is formed on the surface of the substrate. The first reflective microstructure is associated with the first optical port and includes an optically reflective surface. A plurality of second reflective microstructures are formed on the surface of the substrate. Each second reflective microstructure is associated with one of the second optical ports and includes an optically reflective surface. The first reflective microstructure is positionable to orient its reflective surface to reflect an optical signal receivable from the first optical port to the reflective surface of any one of the second reflective microstructures. The first reflective microstructure is also positionable to receive an optical signal reflected from the reflective surface of any one of the second reflective microstructures to the first optical port. Likewise, each second reflective microstructure is positionable to orient its reflective surface to reflect an optical signal receivable from the first reflective microstructure to its associated second optical port and to reflect an optical signal receivable from its associated second optical port to the first reflective microstructure.
The second reflective microstructures may, for example, be arranged in at least one arc with the first reflective microstructure being located on a concave side of the arc. In this regard, the second reflective microstructures may only need to be positionable with one degree of freedom. The second reflective microstructures may be arranged in an outer and an inner arc. Several possibilities exist for providing optical paths between the first reflective microstructure and the reflective microstructures in the outer arc that are not blocked by elevated reflective microstructures in the inner arc. For example, the reflective microstructures in the outer arc may be elevatable to a greater height from the substrate than those in the inner arc (e.g., by using longer lever arms in positioning systems associated therewith). By way of another example, the reflective microstructures in the inner and outer arcs may be arranged such that each is located at different angular locations with respect to the first reflective microstructure with sufficient angular spacing provided between each angular location.
According to a still further aspect of the present invention, an optical cross connect switch includes a support (e.g., a single common substrate) and pluralities of first input mirror microstructures, second input mirror microstructures, first output mirror microstructures, and second output mirror microstructures. The first input mirror microstructures are disposed within a first row on a first side of a first reference axis, and the second input mirror microstructures are disposed within a second row on the first side of the first reference axis in spaced relation to the first row such that the first row is disposed between the second row and the first reference axis. The first output mirror microstructures are disposed within a third row on a second side of the first reference axis that is opposite the first side, and the second output mirror microstructures are disposed within a fourth row on the second side of the first reference axis in spaced relation to the third row such that the third row is disposed between the fourth row and the first reference axis. The optical cross connect switch also includes a first pivot member for each of the first input mirror microstructures, a second pivot member for each of the second input mirror microstructures, a third pivot member for each of the first output mirror microstructures, and a fourth pivot member for each of the second output mirror microstructures. Each first pivot member interconnects its corresponding first input mirror microstructure with the support and is of a first length. Each second pivot member interconnects its corresponding second input mirror microstructure with the support and is of a second length that is greater than the first length. Each said third pivot member interconnects its corresponding first output mirror microstructure with the support and is of a third length. Each fourth pivot member interconnects its corresponding second output mirror microstructure with the support, and is of a fourth length that is greater than the third length. Having the second length greater the first length and the fourth length greater than the third length allows the second input reflective microstructures within the second row to xe2x80x9clook overxe2x80x9d the first input reflective microstructures within the first row and the second output reflective microstructures within the fourth row to xe2x80x9clook overxe2x80x9d the first output reflective microstructures in the third row.
These and other aspects and advantages of the present invention will be apparent upon review of the following Detailed Description when taken in conjunction with the accompanying figures.